Process of sealing evacuated vessels.



PATENTED SEPT. 18, 1906.

W. R. WHITNEY. PROCESS OF SEALING EVAGUATED VBSSELS.

APPLICATION FILED MAB.8, 1905.

Inventor Willis R.Whi'tmeg,

v by

JTb'b'g.

Witnesses:

UNITED STATE PATENT OFFICE.

WILLIS R. WHITNEY, OF ALPLAUS, NEW. YORK, ASSIGNOR TO GENERAL ELECTRIC(JOMPANY, A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Sept. 18, 1908.

A umm am luck 8, not. sum No. 249,109.

To all whom it may concern:'

Be it known that I, WILLIS R. Warmer, a citizen of the United States,residin at Alplaus, town of Glenville, county of So enectady, State ofNew York, have invented certain new and useful Improvements in theProcesses of Sealing Evacuated Vessels, of which the following is aspecification.

In the manufacture of evacuated tubes for mercury-lamps and similarapparatus it has been found desirable to seal up one end of the tubewith a metallic cup. This cup may serve not onl to provide an air-tightclosure for the end 0 the tube, but it ma also serve as a support for anelectrode 0 solid conducting material or as a containing-receptacle foran electrode of mercury. When so used, it-serves to convey current to orfrom the s ace within the receptacle or tube, and there y obviates thenecessit for platinum or other leading-in wires. These metallic cupshave heretofore been sealed to the fragile tubes or vessels b slippingthem over the end of the tube an then heating the cup and the end of thetube until-the glass or other material becomes plastic, after which theglass may be blown against the inner surface of the cup, making intimatecontact therewith and an air-ti ht seal. In carrying out this processconsi erable care must be exercised in selecting a proper thickness forthe metal cup, so that when the tube is allowed to cool after theheating operation the different ratios of expansion of the two materialswill not cause a fracture of the glass or other fragile material. Thusif the metal cap is made too thick and ri id it has a tendency to shearofl the glass tu e at the upper edge of the cup or at least to set upsuch strains in the glass that the tube will fail at this point. On theother hand, if the metal cup is made very thin it is liable to berendered defective by the oxidation which results from the heat appliedduring the sealing operation. As the usual thickness of these cups asheretofore used is about .008 to .012 inches, the corrosion of a vesmall quantity of the metal will greatly re uce the mechanical strengthof the seal. Furthermore, althou h the seal may a pear perfect at thetime o manufacture t e metallic oxid on the surface of the cup mayeventually scale ofl, thus opening 1 materiall up holes through themetal or at least so reducing its stre h as to finally destroy thevacuum within t e tube.

It is the object of this rocess to protect the metal cup from oxidationduring the sealing-in operation, thereby reservingthe original strengthof the metal cup and permitting the use of sheet metal for such cupsthinner than has heretofore been em loye he process consists,essentially, in protecting the metal cu with a covering ofnoncombustible materia such, for instance, as a second metal cupslightly larger than the first and completely surrounding the latter,this second cup being retained in lace until all the heating processeshave con com pleted, after which it may be slipped off, eaving the innercup bright and unimpaired.

The drawing shows a mercury-rectifier with seals constructed accordingto the process aboveoutlined.

In the figure, 1 is a vessel, of glass or other material, capable ofbein rendered ductile by heat. 2 and 3 are tubu ar extensions of thisreceptacle containing anodes 4 and 5, of carbon or other suitablematerial, supported from metallic cups 6 and 7, as will be readilyunderstood by those skilled in the art. The tube is provided with amercury-cathode 8, the mercury being in electrical contact withthe-metalliccup 9. consist of iron, iron alloys, or other suitablemetallic material. A second cup 10, preferably of the same material asthe inner cup, surrounds the latter, thereby protecting it fromoxidation during the heating and sealing operations. In carrying out myprocess these two nested cups are slipped on over the end of the tube,and the tube is subsequently heated and blown out until it makes an air-This metallic cup may tight 'oint with the inner cup. After this the tue ma be allowed to cool and may be sealed off in t e complete form, asshown in the figure. When so completed, the outer cup 10 may be removed,thereby leaving the inner cup 9 unimpaired by the heating and sealingoperations. The other seals for the tube ma be protected in the samemanner during the process of manufacture by the auxiliary cups 11, 12,and 13.

While I have described my improved proc- I as appliedmercuryY-rectifiers it should i be understood that it is equallyapplicable to metal.

disp not disadvantageous any type of 'pparatus in which an air-tightseal is necessary between'an oxidiz able mate rial and a material whichmay be rendered ductile by heat.' a

I am aware that it is old in the manufacture of certain forms ofoil-lamps to secure a metal collartothe glass oil-well by first heatingthe glass and then introducing it into the metal collar. and blowing itout against the In such a process the metal ,issnot" heatedexceptbyradiat-ion'from'the lass, so

i temperature/t an -the glass. The result of this is that when the oint1s cooling a greater contraction occurs in the glass than in the metal,and the glass tends to separate slightly from the inner surface of thecollar. Such a phenomenon is in connection with oillam s, -asthe collarmay be protected. from lacement by annular fiutings or threads. On theother hand, such a process is entirely ina plicable to mercury-vaporlamps, as the slig test leak around the seal-would eventually destroythe vacuum and ruin the lamp. The process forming the sub'ect of thisapplication differs essentially om that just described in severalparticulars, one of which is that in carrying out my process both theglassand the metal cup are heated to substantial-ly thesame temperatureduring the sealing operation, so that both are considerably expanded.Then when the joint cools the higher coefficient of expansion of themetal causes the metal cup to contract more rapidly than the glass,thereby causing the metal to firmly gri the tube. As previously stated,if the meta cup is too thick this powerful-contraction will fracture theglass at the upper edge of the cup; but if, on the other hand, the cupis made of the dimensions described in this application the cup willstretch sufliciently to prevent such destructive action. The thinner themetal cup can be made theless liability there is for destruction of theglass tube from this cause, so that by protecting the sealing-cup with a-heatresisting covering, as herein described, a

eatly-improved article of manufacture can e produced.

'by-Letters-Patent of the and desire to secure United States, is 1. Theprocess of sealing'irangible vessels with a metallic closure, whichconsists-in heating said-closure and. a part of said vessel to atemperature at whic the material of said vessel is plastic, and forcingsaid plastic material into intimate contact with said metallic closureand simultaneously protecting said metallic closure from oxidation witha non-combustible covering.-- A

What- I claim la's new,

with an oxidizable closure, whic consists in -heating said elosifre'anda art of said vessel to a temperature atTWh'ic '-"the"r'1iatenalof" saidvessel is plastic, and forcing said plastic material into intimatecontact with said closure and simultaneously protecting said closurefrom oxidation with a removable metal covering.

3. The process of sealing a frangible tube with a metallic cup whichconsists 1n heatin a part of saidtube to a temperature at which itbecomes plastic, forcing said plastic material against the wall of saidcup,-simultaneously protecting said cup from oxidation with 2.' 'Theprocess of sealing rranfiible vessels a removable covering, andsubsequently re movin said covering.

4. T e process of closing a tubular vessel with a metal cup, whichconsists in mounting a plurality of nested cups on one end of saitubular vessel, heating said; end to a plastic condition and forcin itinto intimate contact with the inner of said cups, and subsequentlyremoving the outer cup.

.5. The rocess of sealin' fragile vessels with meta lic closures whicmultaneously heating said closure and a part of said-vessel to atemperature at which the material ofsaid vessel is plastic, forcing saidplast material into intimate contact with one side of said metallicclosure, and simultaneously protecting the other side of said metallicclosure from oxidation.

In witness whereof I have hereunto set my hand this 6th day of March,1905.

WILLIS R. WHITNEY.

Witnesses:

BENJAMIN B. HULL,

HELEN ORFORD.

consists in si-

